1. Field of Invention
The invention relates to an electrically operated vehicle driving controller, an electrically operated vehicle driving control method and its program.
2. Description of Related Art
In a vehicle drive unit mounted to an electric automobile as an electrically operated vehicle and generating the torque of a drive motor, as an electrically operated machine, i.e., drive motor torque and transmitting the drive motor torque to a drive wheel, the drive motor is conventionally operated by receiving a direct electric current from a battery at a power applying (driving) time and generates the drive motor torque. At a regenerative time (electricity generating) time, the drive motor generates the direct electric current by receiving torque by inertia of the electric automobile and supplies this electric current to the battery.
Further, a planetary gear unit having a sun gear, a ring gear and a carrier is arranged in a vehicle drive unit, mounted to a hybrid type vehicle, as an electrically operated vehicle, and transmits the torque of an engine, i.e., one portion of the engine torque to an electric generator (electric generator motor) as a first electrically operated machine and also transmits the remaining engine torque to a drive wheel. The above carrier and the engine are connected to each other. The ring gear, the drive motor, as a second electrically operated machine, and the drive wheel are connected to each other. The sun gear and the electric generator are connected to each other. Rotations outputted from the above ring gear and the drive motor are transmitted to the drive wheel so that a driving force is generated.
In each of the above vehicle drive units, an inverter is arranged between the drive motor and a drive motor controller. The inverter is operated by a driving signal sent from the drive motor controller and generates the electric currents of U, V and W phases by receiving the direct electric current from the battery and supplies the electric current of each phase to the drive motor. Therefore, the inverter has plural transistors, such as six transistors as switching elements, and each transistor is formed as a unit every one pair and constitutes a transistor module (IGBT) of each phase. Accordingly, when the driving signal is sent to each transistor in a predetermined pattern, the transistor is turned on and off and the electric current of each phase is generated.
The rotating speed of the drive motor, i.e., the drive motor rotating speed, is detected by a drive motor rotating speed sensor. For example, drive motor torque in the drive motor, etc. are controlled on the basis of the drive motor rotating speed.
As the electric generator, the drive motor, etc. are operated, the coil of a stator is heated and the temperatures of the electric generator, the drive motor, etc. are raised so that the characteristics of the electric generator, the drive motor, etc. are reduced.
Therefore, the drive motor rotating speed and the temperature of the drive motor are detected and drive motor target torque, showing a target value of the drive motor torque, is multiplied by a predetermined ratio corresponding to the drive motor rotating speed and the temperature of the drive motor so as to limit the drive motor torque, e.g., as described in JP-A-2000-18402.
However, in the conventional vehicle drive unit, the drive motor target torque is uniformly multiplied by the above ratio when the drive motor torque is limited. Therefore, there is a case in which no drive motor torque can be sufficiently generated and an output required by a driver, i.e., a driver requested output, cannot be sufficiently generated.